#include "apue.h"
#include <netdb.h>
#include <errno.h>
#include <syslog.h>
#include <sys/socket.h>

#define BUFLEN      128
#define MAXADDRLEN  256

#ifndef HOST_NAME_MAX
#define HOST_NAME_MAX   256
#endif

/* figure-16.12.c => figure-16.22.c */
extern int initserver(int, const struct sockaddr *, socklen_t, int);

void
serve(int sockfd)
{
    int              n;
    socklen_t        alen;
    FILE            *fp;
    char             buf[BUFLEN];
    char             abuf[MAXADDRLEN];
    struct sockaddr *addr = (struct sockaddr *)abuf;

    set_cloexec(sockfd);    /* figure-13.9.c */
    for (;;) {
        alen = MAXADDRLEN;
        if ((n = recvfrom(sockfd, buf, BUFLEN, 0, addr, &alen)) < 0) {
            syslog(LOG_ERR, "ruptimed: recvfrom error: %s", strerror(errno));
            exit(1);
        }
        if ((fp = popen("/usr/bin/uptime", "r")) == NULL) {
            sprintf(buf, "error: %s\n", strerror(errno));
            sendto(sockfd, buf, strlen(buf), 0, addr, alen);
        } else {
            if (fgets(buf, BUFLEN, fp) != NULL)
                sendto(sockfd, buf, strlen(buf), 0, addr, alen);
            pclose(fp);
        }
    }
}

/* 无连接的服务器 */
/* gcc apue.h apue_err.c figure-13.1.c figure-13.9.c figure-16.22.c figure-16.20.c -o ruptimed */
int
main(int argc, char *argv[])
{
    struct addrinfo     *ailist, *aip;
    struct addrinfo      hint;
    int                  sockfd, err, n;
    char                *host;

    if (argc != 1)
        err_quit("usage: ruptimed");
    if ((n = sysconf(_SC_HOST_NAME_MAX)) < 0)
        n = HOST_NAME_MAX;
    if ((host = malloc(n)) == NULL)
        err_sys("malloc error");
    if (gethostname(host, n) < 0)
        err_sys("gethostname error");
    daemonize("ruptimed");                  /* figure-13.1.c */
    memset(&hint, 0, sizeof(hint));
    hint.ai_flags = AI_CANONNAME;
    hint.ai_socktype = SOCK_DGRAM;
    hint.ai_canonname = NULL;
    hint.ai_addr = NULL;
    hint.ai_next = NULL;
    if ((err = getaddrinfo(host, "ruptime", &hint, &ailist)) != 0) {
        syslog(LOG_ERR, "ruptimed: getaddrinfo error: %s", gai_strerror(err));
        exit(1);
    }
    for (aip = ailist; aip != NULL; aip = aip->ai_next) {
        if ((sockfd = initserver(SOCK_DGRAM, aip->ai_addr,
                        aip->ai_addrlen, 0)) >= 0) {
            serve(sockfd);
            exit(0);
        }
    }
    exit(1);
}
